Biomedical subjects

Thomas Hansson

Publications and source records attributed to Thomas Hansson.

3 recordsLinked to original sources

PubMed2005

Artificial sensibility of the hand based on cortical audiotactile interaction: a study using functional magnetic resonance imaging.

The capacity of the central nervous system for plastic alterations is the base for our ability to adapt to environmental needs. The crossmodal capacity of the brain makes interaction between senses possible, and deprivation of one sense leads to compensatory changes in other senses. We have recently shown how hearing can substitute for sensation in a transplanted insensitive hand by using a sensor glove equipped with small microphones that pick up the sound of friction, which is elicited by active touch. Here we have used functional magnetic resonance imaging (fMRI) in healthy people to illustrate their capacity for cortical audiotactile interaction with activation of the somatosensory cortex induced by auditory stimuli. The phenomenon occurred only in subjects trained to substitute sensibility by hearing, and no audiotactile interaction was found in untrained subjects.

Acoustic Stimulation↗

PubMed2005

Functional evaluation of regenerated and misrouted low threshold mechanoreceptors and polymodal nociceptors in the skin of rat hindfeet after crush lesions to the sciatic nerve.

Tracer studies on motor axons after nerve crush injuries have indicated that misrouting may occur even when the endoneurium is intact. Misrouting of regenerated polymodal nociceptive C-fibres and low threshold mechanoreceptive axons have been studied functionally in 50 rats three months after unilateral crush lesions to the sciatic nerve. Two weeks before evaluation the tibial fascicle (or the peroneal fascicle) above the lesion was cut and tied off. In this way only functional regeneration of misrouted axons was tested. Misrouted low threshold mechanoreceptive axons and polymodal nociceptor C-fibres were found after regeneration in both glabrous and hairy skin. We conclude that functional misdirection of both myelinated and unmyelinated sensory axons innervating either glabrous or hairy skin can occur after a crush lesion to a peripheral nerve in rats.

Animals↗

PubMed2003

Loss of sensory discrimination after median nerve injury and activation in the primary somatosensory cortex on functional magnetic resonance imaging.

OBJECT: The aim of this study was to assess the effects of median nerve injury and regeneration on neuronal activation in the somatosensory cortex by means of functional magnetic resonance (fMR) imaging and somatosensory evoked potentials (SSEPs). METHODS: Ten injured male patients (mean age 26 years) were examined 15 to 58 months after a total transection of the median nerve at the wrist that was repaired with epineural sutures. Two-point discrimination was lost in Digit II-III and sensory nerve conduction displayed decreased velocity (-29%) and amplitude (-84%) in the median nerve at the wrist. The fMR images were obtained during tactile stimulation (gentle strokes) performed separately on the volar surface of either Digit II-III or Digit IV-V (eight patients: two were excluded because of movement artifacts). The SSEPs were obtained using electrical stimulation proximal to the median nerve lesion. CONCLUSIONS: Patients with loss of sensory discrimination after median nerve damage and regeneration had larger areas of activation in fMR imaging near the contralateral central sulcus during tactile stimulation of the injured compared with the noninjured hand. The increase relative to the unaffected hand was 43% (p < 0.02) for Digit II-III stimulation and 46% (p < 0.02) for Digit IV-V stimulation. The SSEP data showed normal latency and amplitude. The enlarged area of cortical activation may be the result of reorganization, and it may indicate that larger cortical areas are involved in the discriminatory task after a derangement of the peripheral input.

Adolescent↗